In current semiconductor industry, integrated circuit (IC) products can include: logic, memory, and analog circuits. Memory devices take a considerable proportion in IC products. In recent years, flash memories have been rapidly developed. Flash memories can long-termly maintain stored information without supplying power. Flash memories have advantages including high integration degree, fast access speed, and ease for erasing and rewriting. Flash memories are thus widely used in the field of computer, automation control, etc.
With development of semiconductor technology and with more extensive applications of memory devices, the memory devices have to be formed with other suitable devices on a same chip to form embedded semiconductor memory device. For example, when the memory device is embedded in a central processor, the memory device is required to be compatible with the central processor platform and is also required to maintain original specifications and electrical properties.
Generally, the memory device needs to be compatible with an embedded, standard logic device. An embedded flash memory device often includes a logic region and a storage region. The logic region often includes high voltage transistors and low voltage transistors. The storage region often includes a storage unit including a floating gate on a semiconductor substrate surface and a control gate structure on top of the floating gate.
However, it is still desirable to improve properties of the storage unit in the storage region of conventional embedded flash memory devices.